1. Field of the Invention
The present invention relates to a dialog server providing dialogs between users and more particularly, it relates to a method and a computer program for having a conversation in a virtual space.
2. Description of Related Art
Previously, services allowing multiple users to exchange messages and thereby to have a conversation have been provided. Such services include a video conference service utilizing text chat, images and audio. Recently, it is being realized that a large number of users have a conversation in a virtual space. Since each user has been able to exchange messages with a large number of other users, it is necessary to connect each of these other users with his/her messages so that each user can distinguish messages of one user from those of another.
Japanese Patent Application Publication No. 2004-267433 (hereinafter referred to as Patent Document 1) and Japanese Patent Application Publication No. 2007-072511 (hereinafter referred to as Patent Document 2) each discloses a method of processing an inputted speech sound to output a message. According to the method described in Patent Document 1, an inputted speech sound is converted or combined with another sound so as to be closely associated with a virtual space before being outputted as a chat sound. According to the method described in Patent Document 2, a speech sound of a character assigned to a client terminal is synthesized and by using this character's speech sound, speech-sound data corresponding to a message inputted from the client terminal is generated.
Japanese Patent Application Publication No. Hei 9-006985 (hereinafter referred to as Patent Document 3) and Japanese Patent Application Publication No. Hei 10-079929 (hereinafter referred to as Patent Document 4) disclose a method of bringing a user other than a certain user into a view of the certain user. According to the method described in Patent Document 3, a distance between a first avatar a and a second avatar b is measured. If the distance is not more than a threshold value L and the first avatar a looks at the second avatar b, and if the distance is kept not more than a threshold value L for a time period not less than a threshold value T, the second avatar b is rotated in the current position or moved until the first and second avatars a and b look at each other. According to the method described in Patent Document 4, a graphically displayed icon representing a user who participates in a shared 3D space is brought into a view of another user in response to strength and feature quantity of the former user's speech sound.
Japanese Patent Application Publication No. 2001-228794 (hereinafter referred to as Patent Document 5) discloses a method of displaying, in a view of a user, a message of another user at a position varying in accordance with a position of the latter user, if the message is a text message. According to the method described in Patent Document 5, a position in which text-based information to be displayed of a speaker-user is determined on the basis of a distance between the speaker-user and a listener-user, a view of the listener-user, a 3D position of the speaker-user, and a vector indicating speaker-user's line of sight. Thereafter, the text-based information is outputted in the thus-determined position.
If the above conventional techniques are applied to a situation each user exchanges messages with a large number of other users, the following problems will arise. If the large number of other users simultaneously output messages, the methods of Patent Documents 1 and 2 allow the messages to have different tones and sounds. However, it is still difficult to recognize a certain message from these overlapping sounds. If there are a large number of users in a certain area, the methods of Patent Documents 3 and 4 keep the views of the certain user and the large number of other users frequently moving, so that the users have difficulties in continuing conversations. If a large number of messages are simultaneously displayed, the method of Patent Document 5 allows each message to be displayed in a position corresponding to a positional relationship between a listener-user and a speaker-user. However, it is still difficult to distinguish messages of one user from those of another.